WO 2010/126415 discloses a method and apparatus for manufacturing an elasticised web having discrete elastic thread portions separated in a machine or longitudinal direction of the elasticised web. The resulting elasticised web is disclosed to be formed into a front waist region or a rear waist region of an absorbent article and the elastic threads provide front or rear waist region leg elastics. The separation between the elastic thread portions in the machine direction forms a crotch portion in the absorbent article that is free of elastic threads in the lateral direction of the absorbent article, which is often desirable.
FIGS. 1 to 5 of the present application are reproductions of selected figures from WO 2010/126415 and will be discussed in detail in the following as an aid to the reader in understanding the background to the present disclosure and to give an understanding of the preferred application of the present disclosure.
Referring to FIG. 1, there is disclosed a second web 200 and a first web 300 being fed in the machine direction MD. Also fed in the machine direction is at least one elastic thread, preferably a group of 2, 3 or more elastic threads, 500 that is arranged on the second web 200 as a wave extending in the machine direction forming an undulating pattern that goes back and forth in the cross machine direction CD. The group of elastic threads 500 are attached to the first web using a spray of adhesive 250. The undulating pattern and the arrangement of the group of elastic threads 500 is such that portions of the group of elastic threads 500 protrude out from a cross machine direction CD edge 203 of the second web 200 and a cross direction CD edge 303 of the first web 300. Accordingly, the group of elastic threads 500 are arranged as portions overlapping and attached to the second web 200 separated in the machine direction MD by portions protruding from the edge 203 of the first web 200 and the edge 303 of the second web 300. The attached portions of the elastic threads will form first and second leg elastics of an absorbent article when the elasticised web 300 is manufactured into an absorbent article. The unattached portions of the elastic threads 500 are to be trimmed away from the second web 200 so that the attached portions become discrete portions of elastic threads separated and unconnected from one another in the machine direction. The separation between adjacent attached portions of the elastic threads 500 in the machine direction MD provide a location for attachment of an absorbent core 3 from the elastic threads 500.
The unattached portions of the elastic threads 500 are trimmed away using a rotary knife 605 that can be better viewed in FIG. 2. Further details of the elastic trimming means of the prior art are detailed below.
Continuing to refer to FIG. 1, a first web 300 is fed so as to be positioned over the second web 200 and laminated thereto so as to sandwich the attached portions of the elastic threads 500, yet leave the unattached portions protruding from the laminate of the first and second webs 200, 300 for trimming using the rotary cutter 605. The laminate of the first and second webs 200, 300 and the discrete elastic thread portions provide an elasticised web 100 that can subsequently be formed into a front waist region or a rear waist region of an absorbent article.
In order to manufacture an absorbent article from the elasticised web 100, a second such elasticised web 100 can be placed parallel to the first elasticised web 100 yet spaced therefrom in the cross machine direction as shown in FIG. 3. A further web 900 can bridge the cross machine directional space between the first and second elasticised webs 100 to connect them to one another. Similarly, an absorbent core 130 can overlap the first and second webs 100 in the cross machine direction and bridge the space between the first and second elasticised webs 100. A cross machine direction cut C can be made to separate the web absorbent article 100, 900, 130 into discrete absorbent articles and leg holes can be made by stamping out the shaded region S to provide leg contours having leg elastics following the leg contours except at the region overlaid by the absorbent core 130.
Referring to FIG. 2 of the present application, the apparatus and method for trimming the protruding portions of elastic threads can be understood more fully. As can be seen, the second web 200, the first web 300 and the elastic threads 500 are sandwiched together at a nip 400 between rollers. At this stage, the laminate has unattached portions of the elastic threads protruding from a side edge thereof that have yet to be trimmed away. The protruding, unattached portions of the elastic threads 500 are gripped between first and second belts 401, 402, which is perhaps more clearly illustrated in FIG. 1. The unattached, protruding portions of the elastic threads 500 are thus held in position in the cross machine direction and in the machine direction MD so that they are held taut and are manageable during the trimming process. The laminate of the first and second webs 300, 200 and the elastic threads 500 is held against the outer surface of a rotating drum 620 in order to provide a support surface for the laminate and to feed the laminate passed the rotary cutter 605. As can be seen from FIG. 2, the first and second belts 401, 402 are arranged to move correspondingly with the movement of the outer surface of the drum 620 so that the protruding portions of the elastic threads 500 are kept in fixed relation relative to the laminate 200, 300, 500.
With the laminate 200, 300, 500 held against the outer surface of the drum 620 and with the protruding portions of the elastic threads 500 gripped between the first and second belts 401, 402, the rotary cutter 605 is pressed against the outer surface of the drum 620 so as to cut through the protruding portions of the elastic threads 500 at the edge of the laminate 200, 300, 500 in order to trim the unattached portions of the elastic threads 500 to thereby provide the laminate 100 with discrete portions of elastic threads separated in the machine direction.
At least two problems have been found with the press cutting arrangement of the prior art. A first problem is that the engagement between the blade of the rotary cutter 605 and the outer surface of the drum 620 tends to wear at the sharpness of the blade, requiring relatively frequent maintenance to sharpen the blade or relatively frequent replacement of the blade. The other problem is that the deforming nature of the elastic threads 500 tends to result in the elastic threads 500 occasionally not being cut, even if the drum 620 is provided with an elastic backing surface for reception of the blade of the cutter 605. Accordingly, one objective of the present disclosure is to provide a means and method of trimming material away from a web, particularly elastic material and, even more particularly, elastic threads, that is able to reduce a maintenance burden and is also able to ensure a better rate of cutting success of the material.
An alternative method and apparatus for manufacturing an elasticised web for use in manufacturing an absorbent article as disclosed in WO 2010/126415 will be described with reference to FIGS. 4 and 5 of the present application.
In the method and apparatus of FIGS. 4 and 5, a single elasticised web is formed that can be manufactured into an absorbent article by the addition of an absorbent core 130 and a suitable cross directional cutting step and a stamping out step without requiring first and second elasticised webs to be separately formed and connected by a bridging web 900 as in the method and apparatus of FIGS. 1 to 3.
More specifically, second and third webs 200, 700 are fed in side-by-side relation to a nip 400 at which nip the second and third webs 200, 700 are laminated to a first web 300. Sandwiched between the second web 200 and the first web 300 is at least one first elastic thread or a first group of elastic threads 500 attached to the second web 200 and arranged in an undulating pattern 500 as shown above with respect to FIG. 1. Similarly, at least one second elastic thread or a second group of elastic threads 502 is sandwiched between the third web 700 and the first web 300 in a path extending along the machine direction and undulating in the cross machine direction CD. The second and third webs 200, 700 are laminated to the first web 300 in an arrangement separated from one another in the cross machine direction so that the first web 300 is exposed in a central area in the cross machine direction CD. Like in the method and apparatus discussed above with respect to FIGS. 1 to 3, the first and second elastic threads 500, 502 are partially attached to the first web 300 at portions sandwiched respectively between the second and the third webs 200, 700 and the first web 300.
There are also unattached portions of the first elastic threads 500 protruding from the laminate of the second web 200 and the first web 300 and there are also unattached portions of the elastic threads 502 that protrude from the laminate of the third web 700 and the first web 300. These unattached, protruding portions of the elastic threads 500, 502 are to be trimmed away in order to provide the resulting elasticised web 100 with discrete portions of elastic threads 500, 502 that are separated from one another in the machine direction. There is thus provided a row of first discrete portions of the elastic threads 500 extending in the machine direction of the resulting elasticised web 100 and a second row of discrete portions of the second elastic threads 502, where the first and second rows are separated from one another in the cross machine direction and arranged such that the discrete portions of elastic threads 500, 502 are aligned with one another in the machine direction as can be seen in FIG. 5. The unattached portions protrude toward one another in a central region of the first web 300 in the cross machine direction CD where the cross machine directional separation of the second and third webs 200, 700 is located.
In order to trim the protruding, unattached portions of the elastic threads 500, 502, a trimming operation is to be carried out. As with the apparatus and method disclosed with respect to FIGS. 1 to 3, the protruding unattached portions of the first elastic threads 500 are to be grasped between first and second belts 401, 402 and held taut as they are moved with the laminate of webs 200, 300, 700 passed a press cutter 605. The first and second belts 401, 402 are arranged respectively on an upper surface of the first web 300 and a lower surface of the first web 300 such that both the unattached portions of the first elastic threads 500 and the first web 300 are held between the first and second belts 401, 402. The laminate of webs 200, 300, 700 are held against the outer surface of a drum 620 to act as a support surface against which the blade of the press cutter 605 can press in order to cut through the protruding portions of the first elastic threads 500. A second such cutting mechanism 605′ is provided adjacent to the first cutting mechanism 605 in the cross machine direction for cutting the protruding portions of the second elastic threads 502. Again, the laminate of webs 200, 300, 700 is held against the outer surface of the drum 620 and the protruding portions and the first web 300 are gripped between third and fourth belts 403, 404 as they are trimmed away by a second press cutter 605′. Like the first press cutter 605, the second press cutter 605′ is arranged so that the blade thereof presses against the outer surface of the drum 620 so as to cut through the second elastic threads 502.
The resulting elasticised web 100 can be manufactured into discrete absorbent articles by attaching an absorbent core 130 between the discrete portions of elastic threads in the machine direction of the elasticised web 100, cutting the elasticised web in the cross machine direction at C and stamping out material to form leg contours at S. A first row of the discrete elastic portions forms leg elastics for one of a front waist region and a rear waist region of the resulting absorbent article and a second row of the discrete elastic portions forms leg elastics for the other of the front and rear waist regions of the resulting absorbent article. Adjacent discrete portions in the machine direction of the elasticised web 100 ultimately form leg elastics for the left and right legs respectively once the elasticised web is cut and further formed into discrete absorbent articles. The manufacturing method of FIGS. 4 and 5 is more efficient in some ways as compared to the manufacturing method of FIGS. 1 to 3 since the formation of separate first and second elasticised webs 100 that then have to be connected together by a bridge of material is not required. The method of cutting away the unattached, protruding portions of elastic threads 500, 502 is complicated. That is, the first and second press cutters 605, 605′ cannot be pressed against the outer surface of the drum 620 continuously as can be done in the method and apparatus of FIGS. 1 to 3 because this would split the elasticised web 100 into three parts in the cross machine direction CD. Thus, the first and second press cutters 605, 605′ are pressed intermittently against the outer surface of the drum 620 in synchronisation with the elasticised threads so as to cut the unattached, protruding portions of the elastic threads 500, 502 and to intermittently leave the laminate uncut in between the unattached, protruding portions of the elastic threads 500, 502 in the machine direction MD. While this does allow an efficient method and apparatus for manufacturing absorbent articles, the intermittent press cutters 605, 605′ leaves slits in the first web 300 where the elastic threads 500, 502 have been cut. The slits are not always desirable.
Another object of the present disclosure is, therefore, to provide a method and apparatus for trimming material, that is attached to a web, away from the web in a manner that allows the web to be held against a support surface and extend underneath a knife edge for trimming away the material without the web itself also being cut.